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Preexposure prophylaxis (PrEP) could reduce new cases of HIV infection by one-third among men who have sex with men (MSM) over the next decade, according to a new study by researchers at Emory University, US Centers for Disease Control and Prevention (CDC), and the University of Washington. The study, published online today in the Journal of Infectious Diseases, forecasts the broad public health benefits of PrEP, a combination of tenofovir disoproxil fumarate and emtricitabine formulation (sold under the name Truvada) that was approved by the FDA in 2012 for HIV prevention among those at high risk of infection.

A team led by Samuel Jenness, PhD, assistant professor in the Department of Epidemiology at the Rollins School of Public Health at Emory, used mathematical models of HIV transmission among MSM to estimate how many infections would be averted, and how much PrEP would be needed, if the 2014 CDC clinical practice guidelines for PrEP were followed over the next 10 years. These guidelines outline the behavioral and biological indications for good candidates for PrEP. MSM, the group most highly impacted by HIV in the United States, account for approximately two-thirds of all new HIV infections each year.

Based on study results, reducing new HIV infections by one-third over the next 10 years would require that 40 percent of MSM indicated for PrEP (according to the CDC guidelines) were prescribed the daily-oral drug, and most of them took the drug according to instruction. The model estimates that preventing each new HIV infection would require treating 25 men with PrEP for one year. The study also provides disease predictions under conditions in which less MSM are taking PrEP or fewer are taking it daily, as instructed.

“Our study provides the first estimates of the long-term benefits of implementing PrEP according to the CDC guidelines,” explains Jenness. “Our study suggests that the risk indications and clinical monitoring recommendations within the guidelines provide a good balance between epidemiological impact and intervention efficiency. However, to achieve maximal impact will require major efforts to scale-up PrEP to men who need it the most, and long-term adherence management to maintain biological efficacy over time.”

Current data suggest that between 5–10 percent of MSM have recently used PrEP. Because of the uncertainty in PrEP coverage levels and adherence patterns over the next decade, the study provides disease predictions for a variety of scenarios. An online web-based application accompanying the paper, available at https://prism.shinyapps.io/cdc-prep-guidelines, allows for exploration of the paper’s main findings along with these scenarios.